The present invention relates to the development or clean-out of water wells and more particularly concerns such development and clean-out of a newly formed well that has just been perforated.
In many types of well drilling operations well casing is punctured at points below the ground and the openings thus formed must be cleared. In the drilling of water wells, for example, it is common practice to drive the well casing to a desired depth, at or beyond water bearing strata, and then to perforate the casing within the upper and lower boundaries of water bearing strata to provide for flow of water into the well casing.
After perforation of the well casing, the well must be developed, that is, sand and other debris must be driven from the casing perforations and such debris and other particles must be driven from the interior of the casing. Commonly after completion of the perforation the perforating tool is withdrawn from the well and an air-jet nozzle is then positioned within the well to accomplish well development. The withdrawal and subsequent insertion of tools from and into the well are difficult and time consuming processes and can add significantly to the cost, work and time involved in well completion.
U.S. Pat. No. 4,220,201 for Casing Perforator, issued to Earnest D. Hauk, one of the inventors of the present application, shows an air actuated water well casing perforator in which a perforating wheel is mounted on a pivoting arm that is driven into perforating position by an air cylinder and piston. With the wheel in position the entire perforator, by means of the drill string upon which it is mounted, is pulled upwardly to form the perforations. Air is supplied to the perforator actuating piston in this patent via a ball check valve arrangement that is mounted within the perforator piston. Differential pressure is employed in this patent to cause air to alternatively actuate the perforator or to be ejected through ports for well development and clean-out. Pressure below a predetermined amount, such as 80 pounds per square inch, is sufficient to actuate the perforator in this patent but not sufficient to disturb the normally closed check valve. Thus the lower pressure is used for the perforating operation. Higher pressures open the check valve and allow air to be discharged into the interior of the casing.
Although the perforator of the U.S. Pat. No. 4,220,201 effects perforation very satisfactorily, the ball check valve arrangement, designed for the purpose of selectively diverting air pressure for well clean-out purposes, has experienced many problems. It is difficult under field conditions, deep within a drilled well, to provide adequate control of the different pressures required for alternative operation of the perforator tool or the clean-out functions. Partly for this reason, the intended selectively alternative operation of casing perforation and well development is not accomplished satisfactorily with the arrangement of this patent. Further, the perforator may remain with its cutting wheel in cutting position during the desired well development and well clean-out so that is difficult to move the drill string and its assembled tooling within the well as may be desired during the application of the pressurized air for clean-out.
Accordingly, it is an object of the present invention to provide a well developing system that minimizes above-mentioned problems.